Apparatus and method of monitoring the status of a local area network

ABSTRACT

Apparatus for monitoring and displaying the status of a local area network. The network includes a hub with ports for connection to various data terminal equipment in a star configuration and for connection to other hubs of the network. The hubs each have different types of plug-in modules which have ports for connecting the hub to different types of network cable such as fiber optic cable, unshielded twisted pair cable and shielded twisted pair cable. Information is automatically provided to a control console identifying the types of modules and the location of the modules in the hub so that an image of the actual hub can be displayed on the screen of the control console. The actual hub image shows the location and types of modules installed in the hub. In addition, information regarding the connection of each of the hubs to other hubs of the network is obtained and provided to the control console. The information is processed so as to automatically produce a topology map on the control console display showing the overall topology of the network.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to local area networks and moreparticularly to apparatus and methods for monitoring the status of alocal area network by producing a topology map of the networkconfiguration and by producing a control console display image depictingthe appearance of selected network hubs.

2. Background Art

Local area networks for interconnecting data terminal equipment such ascomputers are well known in the art. Such networks may include a largenumber of components which may be configured in a variety of ways.

Although equipment exists for monitoring the status of local areanetworks, such equipment is not capable of accurately monitoring andreporting network status in a manner which may be readily interpreted.For example, the network may include a large number of hubs orconcentrators, each of which form the center of a star configuration.The concentrators may each be capable of servicing a large number ofdata terminal equipment such as personal computers. The network mediummay be shielded twisted pair cable, unshielded twisted pair cable orfiber optic cable or a combination of all three. Further, each type ofcabling may be supported by various types of modules located in each ofthe concentrators.

None of the conventional apparatus for monitoring and displaying thestatus of a network are capable of conveying the actual status of thenetwork in a manner which can be easily comprehended by a user. Thedisclosed apparatus and method overcomes such limitations and allow theactual status of the network to be automatically monitored anddisplayed. The information displayed depicts in great detail the statusof a network which can be easily comprehended by individuals with aminimum amount of training even if the network is relatively complex.Further, the status of the network is automatically updated. These andother advantages of the present invention will become apparent to thoseskilled in the art upon a reading of the Detailed Description of thePreferred Embodiment together with the drawings.

SUMMARY OF THE INVENTION

Apparatus and a method of monitoring the status of a local area networkare disclosed. The network typically includes a plurality of hubs, suchas concentrators, with each hub having data ports for coupling the hubin a star configuration to either data terminal equipment, such aspersonal computers, or for coupling the hub to another hub of thenetwork. The network is of the type which utilizes network contentioncontrol such as the well known Carrier Sense Multiple Access WithCollision Detection (CSMA/CD).

In one embodiment of the invention, the apparatus automaticallydetermines the overall topology of the network, with the hubs having atleast three data ports each. The apparatus includes a transmit meansassociated with each of the hubs having both originate and repeat means.The originate means functions to transmit messages over the networkwhich originate at the associated hub and which contain an identifyingaddress of the associated hub. The repeat means functions to transmitmessages received by the associated hub over the network whichoriginated from other hubs of the network.

Each of the hubs further includes port identifying means for identifyingwhich of the data ports has received one of the messages transmitted byanother hub of the network. In this manner, topology data regarding theconnection of the various ports of the associated hub to other hubs ofthe network are obtained. The topology data from a single hub usuallydoes not contain enough information to ascertain the overall networktopology.

The apparatus further includes control means coupled to the network forreceiving the topology data from each of the hubs in the network. Thetopology data identify a particular one of the data ports of the hubreporting the topology data and address of the other ones of the hubswhich originated network messages received by the reporting hub overthat particular port. Finally, the apparatus includes processing meansfor determining the overall topology of the network utilizing thereceived topology data.

In another embodiment of the invention, the apparatus monitors thestatus of each of the hubs of a star configured network by producing animage, on a control console display for example, which depicts theappearance of the actual hub.

Each hub of the network includes a chassis for receiving a plurality ofmodules. The modules have at least one port for connecting the dataterminal equipment such as a computer to the hub, with the modules beingof varying types. For example, some modules may be adapted for use withunshielded twisted pair cables and other modules may be adapted for usewith optical cables.

The apparatus includes location means for producing location dataindicative of the location of each of the modules in the hub chassis. Anexemplary location means would include hard-wired slot identificationbits located on the chassis which are transferred to any module insertedinto the chassis slot associated with the hard-wired bits. Type meansare further included for producing type data indicative of the type ofeach of the modules in the hub. An exemplary type means would includehard-wired bits on the module which indicate the type of module.

Finally, the apparatus includes display means for producing an image ofthe hub utilizing the location data and the type data, with the imagedepicting the location of the modules in the hub and the type ofmodules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an exemplary local area network of the type inwhich the subject invention can be used and which includes threeconcentrators or hubs and associated data terminal equipment.

FIG. 2 is a schematic diagram of a local area network, havingtwenty-four concentrators, of the type in, which the subject inventioncan be used.

FIG. 3 is an exemplary display produced in accordance with the presentinvention depicting a selected portion of the topology of the network ofFIG. 2.

FIG. 4 is a schematic diagram of a local area network with the upperlevel concentrators connected to a common coaxial cable.

FIG. 5 is an exemplary display produced in accordance with the presentinvention depicting a selected portion of the topology of the network ofFIG. 4.

FIG. 6 is a section of a display menu showing a portion of a main menubar and an exemplary selected submenu.

FIG. 7 is a section of a display showing a detailed view image whichdepicts the actual appearance of the front panel of a selected networkconcentrator, including the location of modules in the concentrator andthe type of modules.

FIGS. 8A-8F are enlarged views of selected portions of the FIG. 7 imageshowing details of the various type of modules.

FIG. 9 is similar to FIG. 7 except that another style of concentrator isdepicted.

FIG. 10 is a block diagram of one of the network concentrators showingthe network management module and host modules all connected to a commonconcentrator backplane together with various data terminal equipment inthe network management control console connected to the concentrator.

FIG. 11 is a block diagram showing the network management interface forthe host modules for interfacing the modules to the concentratorbackplane.

FIG. 12 is a block diagram of a further exemplary network showing theinterconnection of the concentrators of the network.

FIG. 13 is a Network Management Module List showing the various ports ofeach of the concentrators and the addresses of the other concentratorswhich transmit messages received over the ports.

FIG. 14 is a flow chart depicting the process whereby the link data areobtained from the concentrators to construct the FIG. 13 List.

FIG. 15 is a flow chart depicting the process whereby the link data ofthe FIG. 13 List are processed, to form the Ancestor Table of FIG. 16.

FIG. 16 is a Ancestor Table constructed from the data contained in theFIG. 13 List.

FIG. 17 is a block diagram of a network where the up port of the highestlevel concentrators are connected together so that no concentrator willbe assigned the Level 0 position of the topology display.

FIG. 18 is a simplified display image of the overall topology of anetwork based upon the data of the FIG. 16 Ancestor Table.

FIG. 19 is a functional block diagram of the network management modulelocated in each of the network concentrators.

FIG. 20 is a functional block diagram of the control console adapter,the adapter being an expansion card used to convert a personal computerto a network management control console.

FIGS. 21A-21C are flow charts depicting the process for producing thedetailed view of the concentrators such as depicted in FIGS. 7 and 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawings, FIG. 1 is a diagram showing the physicalconnection of a typical simplified local area network. The depictednetwork function to interconnect six personal computers or PCs 20a-f.The network includes three concentrators 22a, 22b and 22c. Theconcentrators function as a hub in the star network topology and providebasic Ethernet functions. Many of the details which will be providedregarding the network are exemplary only, it being understood that thepresent invention may be utilized in connection with a wide variety ofcommunication networks.

Each of the concentrators includes several plug-in modules 26 whichconnect to a backplane (not depicted) of each concentrator 22. There arevarious types of modules including host modules which have ports forconnecting the associated module to data terminal equipment (DTE). Forexample, concentrator 22b includes a host module 26c having a port (notdesignated) connected to personal computer 20a by way of an interfacedevice 24a. Device 24a is a transceiver (transmitter/receiver) used tolink the computer 20a (DTE) or node to the network cable. Module 26cwill typically have several other ports (not depicted) for connecting toother DTEs.

One of the DTEs, such as personal computer 20d, is designated as thenetwork management control console (NMCC). The designated computer 20dis provided with a control console adapter (CCA), which is an expansionboard which adapts the computer for use as a control console. As will beexplained, a user can perform various network monitoring and controlfunctions at the NMCC. A pointer device, such as a mouse 23 havingprimary and secondary control buttons 23a and 23b, respectively, is usedfor carrying out these functions.

Each concentrator 22a, 22b and 22c is provided with a network managementmodule (NMM). The network management module NMM gathers data received ona port of a host module and transmits the data to other modules in theconcentrator. Further, the network management module NMM will forwardthe received data to other concentrators in the network that may beconnected to the concentrator.

The foregoing can be further illustrated by way of example. Assume thepersonal computer 20e has a message for computer 20b. Each computer ornode in the network has an associated address. Messages directed to aparticular computer will be decoded by a conventional network controllercard installed in the computer and, if the destination address in themessage matches the computer address, the message will be processed bythe computer. The message originating from computer 20e will include adestination address of computer 20b. The message will be transmitted tothe associated transceiver 24e and will be received by a port (notdesignated) on host module 26g of concentrator 22c. Module 26g willtransmit the received message to the network management module NMM inconcentrator 22c by way of the concentrator backplane (not depicted).

The NMM will transmit the received message to each host module inconcentrator 22c, including modules 26f, 26g and 26e. The message willexit each port of each module and will be received by transceiver 24dand 24f (but not 24e which received the message originating fromcomputer 20e). However, since the destination address does not match theaddress of computers 20d and 20f, the network controller cards installedin computer 20d and 20f will not process the messages.

The NMM in concentrator 22c will also forward the received message toconcentrator 22a by way of transceiver 24g. The message will be receivedby a port in module 26d and by the NMM in concentrator 22a. The NMM ofconcentrator 22a will transmit the message to the NMM of concentrator22b. The NMM of concentrator 22b will transmit the message to eachmodule in concentrator 22b so that the message will be received bytransceivers 24a, 24b and 24c. Since transceiver 24b has an addresswhich matches the destination address, transceiver 24b will forward themessage to the associated computer 20b. The other two transceivers 24aand 24c connected to concentrator 22b will refrain from forwarding themessage.

Since each message received by a concentrator is retransmitted, only asingle message can be transmitted over the network at one time. In theevent two computers attempt to transmit at the same time, the messageswill interfere and cause a collision in the network. As is well known,when a collision on the network occurs, the concentrator connected tothe two cables on which the collision occurred will detect the presenceof the collision.

When a collision is detected by an NMM, a "jam" signal will betransmitted by the NMM of the concentrator over the network. Thecomputers involved in the collision will detect the presence of thecollided signals and will resort to statistical contention for thenetwork. Other computers not involved in the collision will sense thecarrier signal and refrain from transmitting on the network.

Eventually, the jam signal will disappear and the computers will contendfor access to the network. A computer wishing to transmit first listensfor message traffic on the network and transmits only if there is notraffic and only in the absence of any other carrier signal. This wellknown method of providing access to a common local area network mediumis referred to as Carrier Sense Multiple Access with Collision Detectionor CSMA/CD.

The network depicted in FIG. 1 is relatively small and includes twolevels of concentrators. Concentrator 22a is at the top level (level"0") and concentrators 22b and 22c are at the next from top level (level"1"). It would be possible to connect several additional DTEs, includingcomputers, work stations, servers, and the like to the concentrators22a, 22b and 22c. Further, additional concentrators could be connectedto the exiting concentrators.

FIG. 2 shows how a much larger network consisting of twenty threeconcentrators. None of the port connections to the individual hostmodules in the concentrators are shown. Concentrator 28 is the toplevel, or level "0" concentrator. Concentrator 28 is connected to thenext from top level, or level "1" concentrators 30a-30f. The six level 1concentrators are connected to a total of seventeen level 2concentrators 32a-32g. Note that a lower level concentrator can beconnected to a higher level concentrator by way of a connection to thenetwork management module NMM of the lower level concentrator. It isalso possible to connect the higher level concentrator to a host moduleport in the lower level concentrator.

The network management module NMM performs monitoring and controllingfunctions within the concentrator in which it is located. In addition,the NMM sends status and diagnostic reports to the network managementcontrol console NMCC. Further, the NMM executes commands issued by thecontrol console.

One important function of the network management control console NMCC isto monitor the network topology. As previously noted, the NMCC is adesignated computer of the network which includes a control consoleadapter CCA in the form of an expansion board which is installed in thecomputer. The designated computer uses a graphical user interface, suchas a commercially-available software package called Microsoft Windowssold by Microsoft Corporation of Redmond, Wash. Other commerciallyavailable software packages which provide a window environment similarto Microsoft Windows could be used for the present application.

A principal function of the network management control console NMCC isto monitor the status of the network topology. An important feature ofthe present invention is the ability to automatically acquireinformation regarding the topology of the network so that a display ofthe topology can be generated and automatically updated to reflectchanges in the network.

FIG. 3 is an image, generally designated by the numeral 36, which willbe produced on the NMCC video display terminal showing the topology ofthe exemplary network depicted in FIG. 2. The display is a menu-drivengraphics display which uses a pointing device such as a mouse, light penor the like. Referring to FIG. 3, the rectangular boxes depicted in thedisplay are concentrator icons 34a-34e 34e which represent theconcentrators in the network. The screen is only capable of displaying arelatively limited number of concentrator icons at a time. Accordingly,it is necessary to scroll the display to depict all twenty four of theconcentrators, as will be explained.

Concentrator icon 34a corresponds to concentrator 28 in FIG. 2. Icons34b-34g represent concentrators 30a-30f of FIG. 2. The iconsrepresenting the remaining concentrators 32a-32g can be viewed only byscrolling the display both horizontally and vertically.

Display 36 is split between a "Level 0" and a "Level 1". Concentratoricon 34a is shown in the upper "level 0", with the remainder of theicons located in the lower half or "level 1" portion of the screen. Thedisplay can be scrolled vertically by placing the cursor icon or mousepointer 38 over one of the triangle-shaped elements 40 and "clicking" onactuating the control button mouse. When the mouse is clicked, thedisplay will replace the "Level 0" icon at the top with the level "1"icons and replace the "Level 1" icons at the bottom with "Level 2"icons. Since there are a total of seventeen "Level 2" concentrators32a-32g (FIG. 2), it will be necessary to scroll the displayhorizontally to view all of these concentrators. Scrolling to the leftis accomplished by "clicking" left arrow symbol 40a using the mouse andscrolling to the right is accomplished by "clicking" right arrow symbol40b using the mouse.

Concentrator icon 34a displays various information regarding the statusof concentrator 28 (FIG. 2). The chart recorder image displays theamount of message traffic received by the concentrator over time. Thedesignation "000081000002" represents the concentrator identification oraddress. The designation "Normal" indicates the overall status of theconcentrator. The designation will change to indicate a fault or warningcondition.

The designation "2 Levels Below" on icon 34a indicates that two levelsof concentrators are located below the "Level 0" of concentrator 28,namely "Level 1" and "Level 2". The designation "3000" indicates thetype of concentrator. Other concentrators, such as the concentrator 34e,are Model "1000" type concentrators, which have fewer capabilities thando Model "3000" concentrators. Finally, the designation "23Concentrators Below" indicates that there are twenty three concentratorsconnected either directly to concentrator 28 or indirectly toconcentrator 28 through other concentrators.

Each concentrator icon in the lower part of the display 36, in this casethe "Level 1" part of the display, has a vertical bar referred to as alinkage bar. The linkage bar such as bar 42 above icon 34b indicates theconnection between the concentrator and the parent of the concentratorlocated in the next higher level.

The information depicted by the linkage bar and associated text dependsupon the type of concentrator. For example, linkage bar 42 depicts theconnection between the Level 1 Model 3000 concentrator 30a (FIG. 2) andthe Level 0 Model 3000 concentrator 28. For the Model 3000 concentratorlinkage bar 42, the upper tag "2-1" indicates the slot number in whichthe module is located in the concentrator and the port number on thatmodule. In other words, concentrator 28 (FIG. 2) is connected toconcentrator 30a by way of port number 1 of a host module which islocated in slot 2 of concentrator 28. The lower tag "2" of linkage bar42 indicates the slot number of the Model 3000 module which provides theconnection. In the event the module is a network management module (NMM)there is only one port, therefore only the slot number of the NMM isdepicted. If the module was a host module, the slot and port numberswould both be depicted.

Linkage indicator 44 shows the manner in which a Model 1000 concentrator30d is connected to concentrator 28. Model 1000 concentrators areinterconnected by way of the concentrator backplane, abbreviated "BkP1"and by way of an up-port, abbreviated "UpPt". Accordingly, indicator 44shows that concentrator 30d (FIG. 2) is connected to concentrator 28 byway of a cable connected between the up-port of concentrator 30d andport 4 of a module located in slot 2 of concentrator 28.

Only one concentrator icon at a time can occupy the Level 0 position ofthe display. In the typical "star" network topology, the networkbranches out from one central unit in an inverted tree hierarchy. Theupper level usually displays a concentrator icon. However, the topologymay have two or more concentrators linked in parallel at the top levelof the network. In that case, there will be no concentrator icon in theLevel 0 position.

FIG. 4 shows a network topology with seven concentrators 46 connectedtogether at the top level in parallel. The common connection may be, forexample, a coaxial cable 48 which forms a "backbone" of the network. Inthis case, no single concentrator occupies the Level 0 position of thedisplay, as can be seen in the display 50 of FIG. 5. Display 50 reflectsthis topology by leaving Level 0 empty and places the concentratorslinked in parallel in Level 1. Note that the linkage bars carry a toptag with the description "??-??" to reflect the fact that there are noconcentrators located above the Level 1 concentrators.

One of the network concentrators is connected to the personal computerwhich functions as the Network Management Control Console NMCC. As shownin FIGS. 3 and 5, the concentrator which is connected to the NMCC isdesignated on the display screen with a small icon 51 which resembles apersonal computer.

As previously noted, the Network Management Control Console (NMCC)provides a user interface for monitoring and controlling networkoperations. The interface is a menu-driven display running in aMicrosoft Windows environment.

Menu selections are made using a selective technique which is standardto Microsoft Windows pull-down menus. First, the mouse cursor 38 isplaced over the name of the desired selection on the menu bar. As can beseen in FIGS. 3 and 5, the menu bar 52 is located at the top of thedisplay and includes selections or functions "FAULT", CONFIGURATION","PERFORMANCE", "SECURITY", AND "LOG".

The mouse cursor 38 is positioned over the desired selection or functionon the menu bar 52 and the primary mouse button is actuated. This actioncauses a submenu to be displayed. For example, if the "FAULT" functionis selected, the submenu 53 shown in FIG. 6 is displayed immediatelybelow the main menu selection. As can be seen, there are sevensubfunctions or selections in the "FAULT" submenu. A particularsubfunction is selected by dragging the mouse with the primary buttonstill actuated. This action caused sequential subfunctions in submenu 53to be highlighted. When the desired subfunction is highlighted, themouse button is released thereby selecting the subfunction. A check mark(not depicted) will appear in the display next to the selectedsubfunction and will remain there until another function/subfunction ischosen.

The next step is to select a target object for the previously-selectedfunction or subfunction. This is accomplished by positioning the mousecursor over the target object on the screen. For example, if it isdesired to monitor message traffic for a particular concentrator in thenetwork, the DIAGNOSTIC subfunction depicted in FIG. 6 is selected.Next, the mouse cursor is positioned over the target object, such as theconcentrator icon 34b in FIG. 3. In particular, the cursor is positionedwithin the identifier button 43 of icon 34c which contains theconcentrator identifier "000081001001". The primary mouse button is thenactuated thereby raising a pop-up window to appear or a portion of thedisplay depicting an detailed view of the front panel of the selectedconcentrator.

FIG. 7 is an exemplary pop-up detailed view window 56 which is displayedwhen a concentrator is selected. Window 56 occupies a relatively smallportion of the display screen, and the position of the window on thedisplay can be changed as desired. The image which appears in window 56represents the physical appearance of the front panel of the actualconcentrator represented by icon 43.

The concentrator image 56 shows that the concentrator includes thirteenplug-in modules the front panels of which are represented by imagesections 60a-60m. The modules depicted are exemplary only and it ispossible to interchange modules and delete modules as required by thelocal area network. Each concentrator must include at least one NetworkManagement Module NMM. If one or more modules are deleted, one or moreempty concentrator slots will be depicted.

Concentrator image section 60a depicts the front panel of a primaryNetwork Management Module NMM of the concentrator which is shown to belocated in the left most position in the actual concentrator. Thisposition is referred to as slot 1 of the concentrator. Image section 60bdepicts the front panel of another type of Network Management Module NMMwhich functions as a backup in the event the primary NMM fails and islocated in slot 2. Image sections 60c-60l depict internetworking andhost module front panels located is slots 3 through 12, respectively.Finally, image section 60m depicts the front panel of the power supplyfor the concentrator.

FIG. 8A is an enlarged view of the Network Management Module imagesection 60a. The image includes a depiction of the front panel mountingscrews 62a. Also depicted is the inserter/extractor bar 62b and themodel designation "3314M-ST" at location 62c. The model designationrepresents the Model 3314M-ST Network Management Module. The modeldesignation indicates that the NMM and hence the concentrator in whichthe NMM is installed is a Model 3000 rather than a Model 1000

Image section 60a also depicts three light emitting diodes (LEDs)labeled "STA", "PAR" and "NMC" at location 62d. LED "STA" represents agreen LED which is illuminated when the associated module is functioningproperly. Should the module lose power or experience another type ofmonitored function failure, the LED will be turned off. The image of the"STA" will be a rectangle filled with green to indicate that the actualLED is illuminated and will be filled with black when the LED is off.

The LED labeled "PAR" is yellow and is illuminated (shown in yellow)when the NMM has been disconnected or partitioned from the concentratorbackplane. If the module is partitioned, the backup NMM depicted inimage section 60b will function as the primary NMM. In the event thereis no backup NMM, a partition of the NMM will cause the entireconcentrator to be removed from the network.

Image section 60a further depicts a pair of fiber optic connectors atlocation 62e which are standard ST-type bayonet connectors. The topconnector is for receiving data and the bottom connector is fortransmitting data. The two connectors function together as a port forinterconnecting concentrators. The concentrators can also beinterconnected by way of host module ports if the concentrator is Model3000 type concentrator.

Two LEDs are depicted at location 62f, with a yellow LED labeled "P"being illuminated when the port has been partitioned or disconnected.The LED labeled "L" is a green link status indicator which isilluminated when the receiving terminal of the port is connected to atransmitting device in another module. The LED "L" will not beilluminated (will be shown in black) if the transmit and receive opticalcables are reversed.

Section 62g includes a depiction of seven LEDs, two of which are labeled"ONL" and "P/S" green. The LED labeled "P/S" and indicates whether theNMM is acting as the primary or secondary NMM. The "P/S" LED is greenand is illuminated when the NMM is the in the primary mode. The LEDlabeled "ONL" is green and indicates when the NMM is on line. The "ONL"LED image flashes when the NMM has not received software downloaded fromthe CCA and is illuminated steadily when the software download hassucceeded. The top three LEDs relate to network traffic. In the actualmodule, the top LED, which is yellow, is illuminated for 250 ms when acollision is detected in the concentrator. The second from top LED,which is green, is illuminated while data are present in theconcentrator. The third from top LED is green and is illuminated for 250ms after each data transmission. The fourth from the top LED is a greenmicroprocessor fault indicator which shows the status of themicroprocessor in the NMM.

A nine pin male type DB-9 connector is depicted at location 62g ofsection 60a which functions as a service port. Location 62j includes acircular element which represent a microprocessor reset button on theactual module. Location 62k includes a rectangular element whichrepresents a switch which allows termination of the connector at imagesection 62i. Finally, locations 62h and 62i represent type RJ45 femaleconnectors for connection to unshield twisted pair (UTP) cable. Theconnector at location 62h is for a serial port for out-of-bandcommunication between concentrators (NMMs) and the connector at location62i is for connection to an internal modem for out-of-bandcommunication. Out-of-bond communication is communication separate fromthe primary network communication paths and may be, for example, atelephone line.

FIG. 8B is an enlarged view of image section 60b of FIG. 7 which depictsthe backup or secondary Network Management Module. The image issubstantially identical to image section 60a with a few minorexceptions. At location 64a, the designation "3314-ST" appears whichrepresents the Model 3314-ST Network Management Module. The Model3314-ST includes an additional connector, the image of which is depictedat area 64b. The connector is a D13-25 type interconnect and functionsas a standard RS-232 serial port for out-of-band connection to atelephone network. The telephone network can be used to communicateout-of-bond with the NMM in lieu of the standard network (CSMACD)communication path.

The image section 60c of FIG. 8C depicts an internetworking module. Thedesignation "3323" of area 66a of the image indicates that the module isModel 3323. The module is a local bridge which functions to interconnecttwo local area networks of the same type. The local bridge will onlypass traffic that originates in one segment of the network and isintended for the other network segment.

Front panel image 60c includes a region 66c which depicts a fifteen pinD type female connector for connecting the module to an Attachment UnitInterface (AUI) device. An AUI is a standard logical, electrical andmechanical interface for connecting Data Terminal Equipment (DTE) suchas a personal computer, server and the like to the network. Region 66dincludes ten LEDs which provide static and dynamic status conditions ofthe internetworking module.

The image section 60f of the FIG. 7 image is shown enlarged in FIG. 8Ddepicting the front panel of a host module. The upper region includesthe designation "3304-ST" which indicates that the model is a Model3304-ST host module. The image depicts a total of six ports forconnection to up to six DTEs. As shown in region 68b, each port isrepresented by the image of two ST-type bayonet optical fiberconnectors, with the top connector for receiving data and the bottomconnector for transmitting data. The designation "P" and "L" and theimage of two LEDs in region 68c correspond to the image and designationin regions 62e and 62f of the image section 60a of FIG. 8A.

FIG. 8E is an enlargement of the image section 60d of FIG. 7. Thedesignation "3302" at region 70a of the image indicates that thedepicted module is Model 3302 host module. A total of six ports aredepicted for connection to up to six DTEs. As shown in section 70c, eachport is represented by an image of a nine pin type DB-9 connector forconnecting to a shield twisted pair (STP) cable.

Region 70b includes the standard LEDs "STA", "PAR" and "NMI". Inaddition, the region includes six pairs of LEDs, with one pairassociated with one of the six ports. The LEDs labeled "P" are a yellowLED which indicate, when illuminated (shown in yellow), that theassociated port has been partitioned or disconnected from the network.The LEDs labeled "L" is a green LED showing the link status. If the portis connected to a compatible transceiver or network interface card, theLED is illuminated (shown in green). If the port is not connected, theLED turns off (shown in black) and an autopartition takes place,automatically partitioning the port so that the associate LED "P" willturn on.

An enlargement of image section 72b is shown in FIG. 8F. The designation"3305" at region 72a of the image section indicates that the module is aModel 3305 host module. The host module has twelve ports depicted bytwelve images of a connector. The image of the connector associated withthe first port is at region 72c. The image is of a standard RJ-45modular female connector for connection to unshield twisted pair (UTP).There are twelve pairs of LEDs depicted in region 72b, with one pair ofLEDs associated with one of the twelve ports. The function of the twelveLED pairs labeled "P" and "L" is the same as the LED pairs bearing asimilar label in region 70b of FIG. 8E.

The image 60m of the front panel of the concentrator power supply (FIG.7) also includes an image of a status LED which is illuminated (shown ingreen) when the power supply is producing the specified voltages.

There are various specific objects in the concentrator image which auser can select using the mouse pointer. In doing so, the user canselect the object of the function or subfunction, as depicted in FIG. 6,which was previously selected.

There are three category of concentrator objects which can be selected,including the overall concentrator, a particular module in theconcentrator, or a particular port of a particular module.

The overall concentrator object is selected by placing the mouse cursor38 over the image 60a of the primary network management module NMM ofthe concentrator of the detailed view concentrator image 56 of FIG. 7and actuating the primary mouse button. Assuming that the subfunctionDIAGNOSTIC had been previously selected, diagnostic informationregarding the entire concentrator will be displayed. This includes, forexample, specific data packet errors, such as alignment errors, in theconcentrator. Data packets are a form of data structure for Ethernetcommunication and alignment errors are errors which occur when areceived frame does not contain an integer number of bytes. A frame is apackaging structure for Ethernet data and control information.

If a particular module is to be selected, the mouse cursor 38 ispositioned over the top portion of the desired module. Note thatselecting the primary network management module is equivalent toselecting the entire concentrator, as previously noted. When this occursa small window formed from dashed lines automatically appears therebyindicating to the user that the cursor has been positioned in an activeimage location. As can be seen in the upper portion of image 60d of FIG.7, a window 74 will enclose the image of the model number and the statusLEDs for the module if the mouse cursor is positioned in that image areaand the secondary button actuated. If the primary mouse button is thenactuated, the module is selected as an object. Thus, if the subfunctionis DIAGNOSTIC, diagnostic information regarding the module representedby image section 60d will be displayed. Such information may include,for example, packet alignment errors received by all ports on themodule.

If a particular port is desired, the mouse cursor is positioned over theimage of the port. A window will then appear, such as window 75 (FIG. 7)associated with port number 6 of the module depicted by image section60f. As another example, if port number 1 of the module depicted byimage section 601 is selected, a window 76 will appear as shown. If theuser then actuates the primary mouse button, diagnostic informationregarding the selected port will be displayed. Such informationincludes, for example, packet alignment errors received by the port.

FIG. 9 shows an image 78 of a different style of concentrator, referredto as the Model 3030, which can accommodate up to four plug-in modules.Again, image 78 depicts the physical appearance of the front panel ofthe actual concentrator. Image section 80c shows the power supplysection of the concentrator, with two status LEDs with the associateddesignation "Power" and "FAN" being depicted. The "Power" LED is showngreen when the D.C. power is at the proper voltages. The "Fan" LED isshown yellow in the event the fan speed falls below a minimum rate ofrotation.

The four exemplary plug-in modules are mounted horizontally in the Model3030 concentrator, as can be seen in FIG. 9. Image section 80brepresents a Model 3314M-ST Network Management Module which is the samemodule depicted in image section 60a in FIG. 7. Image section 80c, 80dand 80e of FIG. 9 depict modules Models 3314-ST, 3304-ST and 3305 whichare the same modules depicted in image sections 60b, 60f and 60g,respectively, of FIG. 7. The user can select the entire concentrator, aparticular module (slot) and a particular port using a mouse in the samemanner previously described in connection with the image shown in FIG.7.

A functional block diagram of a typical concentrator 28 is shown in FIG.10. As previously described, each concentrator includes a chassis whichreceives several plug-in modules which are inserted in adjacentconcentrator slots. Each module is provided with a rear connector whichengages a common concentrator backplane 82 which is located along theentire rear portion of the concentrator. Backplane 82 includes a set ofelectrical connections which form a CSMA/CD bus 84. The backplanefurther includes several electrical connections which form a control bus86. The CSMA/CD bus is similar to an Ethernet network coaxial cablewhich carries conventional 10 Megabit Manchester encoded digital signalsof the type distributed throughout the entire network. The control bus86 of the concentrator backplane enables the concentrator NetworkMonitor

Module 88 to communicate with the other modules in the concentrator,including host modules 90a through 90b (only two host modules are shown)

The host modules 90a-90b each has one or more ports which can beconnected to Data Terminal Equipment DTE 91 as shown in FIG. 10. When aparticular DTE transmits data over the network, the CSMA/CD signal isreceived by a port and is transferred by the host module associated withthe port to the CSMA/CD bus 84 of backplane 82. NMM 88 receives theCSMA/CD signal by way of data steering logic (DSL) represented by block90. The logic is capable of receiving data from CSMA/CD bus 84 andtransmitting data onto the bus. The other modules in the concentrator donot receive the CSMA/CD data at this time.

The received CSMA/CD data are transferred to a repeater and retimingunit (RRU) represented by block 92. As is well known the RRU retransmitsthe CSMA/CD data. In doing so it is necessary to retime the data toaccount for the distortion inherent in the transmission link.

The RRU 92 transfers the retimed CSMA/CD data back to the data steeringlogic DSL 90 which places the CSMA/CD signal back on bus 84. The othermodules in the concentrator are configured to receive the repeatedCSMA/CD data. The repeated CSMA/CD data are also transferred to thenetwork by way of media dependent adapter MDA represented by block 94.The output of the MDA on line 102 will connect the CSMA/CD signal to theappropriate transmission media, such as fiber optic cable, unshieldtwisted pair (UTP) or shield twisted pair (STP). Line 102 can beconnected to another other concentrator of the network so that theentire network will receive the CSMA/CD data. Other concentrators canalso be connected to the subject concentrator by way of the host moduleports.

Each module in concentrator is connected to the control bus 86 of thebackplane by way of a Network Module Interface (NMI), including NMI 106in the Network Management Module (NMM) 88 and NMIs 107 in the varioushost modules 90a-90b.

The NMM 88, which includes a central processor unit and associatedmemory, as will be described, monitors and controls the other modules inthe concentrator by way of control bus 86. Typically, the other modulesin the concentrator are not required to contain any form of processor,with the "intelligence" of the concentrator management function residingalmost exclusively in the NMM 88.

A Network Management Control Console NMCC 93 is connected to port 2 ofhost module 90b. As previously explained, the NMCC is typically apersonal computer having a graphic user interface 93b and a controlconsole adapter CCA 93c in the form of an expansion card located in thecomputer.

The NMM can control the various modules either in response to commandsreceived by the NMM over the network which originate from the NetworkManagement Control Console NMCC 93. For example, the user at the NMCCcan command the NMM in a particular concentrator to reset the entireconcentrator or reset a particular module or port. The RESET subfunctiondepicted in FIG. 6 is first selected by the user. Next, the expandedview image of the desired concentrator is displayed as depicted in FIGS.7 or FIG. 9. The user can then select the desired object including theentire concentrator, a particular module or a particular port using themouse. The previously-described LEDs on the concentrator modules willindicate in some predetermined manner whether the reset command wassuccessful.

The user can also use the NMCC to initiate a loopback test wherein atest packet is transmitted over the network to a selected concentratorand the concentrator is instructed to transmit the test packet back tothe NMCC. The user first selects the "LOOP BACK" subfunction shown inFIG. 6. Next, the user selects the concentrator to be tested. The NMCCthen verifies communication between itself and the selected concentratorby transmitting a data package to the concentrator which is echoed backby the concentrator to the NMCC.

The NMCC 88 can also monitor the status of a particular concentrator,module or port. The user first selects the STATUS subfunction asdepicted in FIG. 6. Next, the user selects the object using the expandedview of the concentrator as shown, for example, in FIG. 7 or 9. A statusreport regarding the selected object is then displayed in a pop-upwindow. If the selected object is a concentrator, the report willindicate, among other things, whether the retiming unit, such as RRU 92in FIG. 10, is functioning properly. If the selected object is a module,the status report will indicate whether the module power supply isfunctioning properly, whether the module has been enabled or disabled,and whether the Network Monitor Interface NMI, such as NMI 107 in FIG.10, is functioning properly. If a port has been selected, the statusreport will indicate whether the port is active or has been partitioned.Other information can be included in the status reports, if desired.

A functional block diagram of the Network Management Interface NMI 107for interfacing the host modules to the control bus 86 of theconcentrator backplane 82 is shown in FIG. 11. The NMI 107 includes astate machine for transferring network management interface data betweenthe host module and the control bus 86. Typically, the NMM issues acommand by way of the NMM Network Management Interface NMI 106 to one ofthe host modules over the control bus and the recipient host moduletransmits a response back to the NMM over the control bus.

Block 92 represent a sequential state machine which transfers eight bitsof interface data between the host module and the control bus. Statemachine 92 is preferably a gate array although other types of circuitrycould be used. A bidirection buffer 94 is connected to eight lines ofthe control 86 bus through eight pins (not depicted) on the rearelectrical connector of the host module. The eight bidirection lines 96each carry one of the eight bits of Network Management Interface Data(NMIDAT).

Lines 96 are connected to the input/output of the bidirectional buffer94. Another set of buffer input/output lines are connected to the statemachine by way of eight bidirection data lines 98. Data are transferredthrough buffer 94 either from the control bus 86 to the state machine orfrom the state machine to the control bus, depending on the status ofthe direction line 100 controlled by the state machine.

Various timing and control signals are produced by the NetworkManagement Module, NMM, on three lines, collectively designated bynumeral 102. Timing and control signals DENL, RD/WRL and DAT/CMDL areused for transferring the interface data on lines 96 between the NMM andthe host modules over the control bus 80.

Each slot of the concentrator, which is capable of receiving a plug inmodule, is assigned a unique slot identification number. The four bitsof slot identification (Slot ID) on lines 104 are produced by hardwiring (strapping) selected ones of four connector pins of the slot toeither high or low logic levels. The four slot identification bits aretransferred to the state machine 92 on four lines designated by thenumeral 104. The state machine 92 uses the slot identification bits todecode commands from the NMM transmitted over the control bus which isdirected to the particular module which is inserted in the identifiedslot.

The four bits of slot identification are also transferred toprogrammable array logic device (PAL) 106. PAL 106 also receives signalsfrom each of the twelve ports of the modules over twelve separate linedesignated by the numeral 108. If a particular port is active (receivingdata over the network), the appropriate one of the twelve lines will goto a logic high level. If the particular module in the slot has lessthan twelve parts, not all of the lines will be used. PAL 106 includescircuitry for encoding the signals from the port and producing a fourbit port identification code on four lines designated by the numeral112. The code uniquely identifies a particular port receiving data overthe network.

When one of the port activity lines 108 is active, PAL will produce theappropriate port identification on lines 112 and will also transmit theslot identification code IDOUT on four lines 110. As will be describedlater, this information is received by the NMM and eventuallytransferred to the Network Management Control Console NMCC and is usedto automatically generate the topology of the network.

State machine 92 receives eight bits of module identification code onlines 134 and four bits of module revision code on line 132. Theidentification code and revision code identify the module model numberand revision number. The codes are produced in the module by hard wiringthe appropriate lines in the module itself to either a logic low orlogic high signal. The model and revision identification codes aretransferred to the NMM, when requested by the NMM, over data lines 96.This information is eventually forwarded by the NMM to the NetworkManagement Control Console and is used to produce the expanded viewimages, such as depicted in FIGS. 7 and 9.

As previously described, the Network Management Control Console NMCC cancommand the concentrator, modules and ports to provide certain statusinformation. The NMM in the appropriate concentrator receives thecommands over the network and issues commands to particular modules overthe control bus 86 in response to the NMCC command or in respond tocommands originating in the NMM itself.

One command requests the status of a particular module, with the commandcontaining the slot identification number or address of the module. Thestate machine of the Network Management Interface 107 in the host modulereceives and decodes the command and provides the requested statusinformation. This information includes the module identification andmodule revision (module type information) originating on lines 132 and134. Lines 130 Carry four status bits which can also provided to theNMM. One of the four status bits is the state of the status LED locatedat the top of the front panel of the majority of the plug in modules, asshown in region 62d of FIG. 8A. The green status LED is illuminated(depicted in green) if the module is powered and if other basic modulefunctions are proper.

The NMM can also issue commands in response to the Network ManagementControl Console to reset the module as previously described. If thestate machine detects a reset command on the control bus 86 directed tothe module, the state machine will produce a reset signal on line 128.

A module disable command can be issued by the NMM to disconnect orpartition the entire module from the network. As previously described,this command can be issued by the NMM in response to a commandoriginating from the Network Management Control Console. When thiscommand is detected by the state machine on the control bus 86, adisable signal is produced on line 126 and the module is partitioned. Aswill be described later, the other commands can be used to disable orpartition individual ports.

The NMM can also issue a watchdog activity pulse command. When thiscommand is received, a watch dog signal is produced on line 124. Thesignal is typically used to rest a count-down timer on the module. TheNMM is programmed to periodically issue the watchdog command at asufficient frequency so as to prevent the counter from counting downcompletely. If the counter does count down completely, this is typicallyan indication of a fault condition. If this condition is detected, theNMM is reset.

The state machine 92 is also capable of detecting commands which areunique to the particular type or kind of module. For example, a commandcan be issued which will disable or partition a particular port. Sincethe number of ports on host modules differ, it is necessary to constructunique port partition commands for different module types. Also,different types of status commands can be transmitted by the NMMrequesting status data unique to a particular type of module, such asthe status of various LEDs located on the front panel of the module.

Eight bidirectional data lines represented by numeral 114 are connectedto the state machine 92 for providing data to support the uniquecommands. Data are read out of the state machine on lines 114 when theread/write signal RD/WR on line 118 is high. Data can be transferred tothe machine if the signal on line 118 is low.

The five lines designated by the numeral 116 are network managementfunction NMFC decodes which are produced in response to various uniquecommands received by the state machine. The decodes are used to controllogic circuits on the module in a predetermined manner, depending uponthe type of command and the module type. The decodes are ten bits, withthe signal HBEN on line 120 indicating when the five bits on lines 116are the high or most significant bits. The signal LBEN on line 122indicates when the five bits on lines 116 are the low or leastsignificant bits.

As previously described, the network topology is displayed at theNetwork Management Console 93. The topology is produced automaticallyand is updated automatically in the event the network configuration isaltered.

FIG. 12 is a block diagram of one exemplary network depicting thetopology of the network. The exemplary network includes a total of eightinterconnected concentrators 100, 102, 104, 106, 108, 110, 112 and 114.Each concentrator is provided with a Network Management Module. Thenetwork is monitored and controlled by a Network Management ControlConsole NMCC (not depicted) which can be a part of a DTE associated withany one of the network concentrators.

The depicted network includes a mix of two types of concentratorsincluding both Models 1000 and 3000. As previously described, the Model1000 is less flexible than the Model 3000 type. The Model 1000 includesan NMM which can distinguish only two ports. There is an Up Port whichrefers to the connection of the NMM to the Media Dependent Adapter(MDA). There is the Down Port which collectively refers to all of theports on the host modules of the concentrator. The Model 1000 NMM cannotdistinguish between different host module ports.

The Model 3000 concentrator includes the capability of distinguishingbetween the individual host module ports and can identify the particularport number and slot number on which a message is received on thenetwork. The operation of this feature was previously described inconnection with the Network Management Interface (NMI) of FIG. 11. TheModel 1000 NMMs can be connected Up Port to Up Port, but Down Port toDown Port connections are not allowed. The Model 3000 NMMs are moreflexible and can be connected by way of any of the ports of theconcentrator.

The Control Console Adaptor (CCA) of the Network Management ControlConsole (NMCC) is responsible for building and maintaining the topologyof the network. The CCA interacts with all of the Network ManagementModules over the network through a sequence of protocol frames referredto as Protocol Data Units (PDUs).

The CCA also exchanges messages with the User Interface (UI) 93c (FIG.10) of the personal computer of the Network Management Control Console.The User Interface (UI) includes the Windows graphic user interface. TheCCA communicates with the User Interface by way of a Memory ResidentDriver (MRI) on the personal computer and converts the PDU formats toand from the User Interface.

Each of the Network Management Modules (NMMs) includes a processor andassociated memory, as will be described. The NMM processor executes codein a local RAM which is downloaded from the CCA of the NMCC to each ofthe NMMs.

The sequence for producing the initial network topology will now bedescribed. Initially, the Control Console Adapter (CCA) transmits aProtocol Data Unit (PDU) over the network to each of the network NMMs.The PDU, called Loadserver Ready, is transmitted every five seconds andindicates to the NMMs that the CCA is ready to download code to each ofthe NMMs.

After power up, all of the NMMs listen for the Loadserver Ready message.Once the message is received, the NMMs request the CCA to download theirrespective code.

Following download, all of the NMMs transmit what is referred to as aHello PDU or message over the network. The Hello message is transmittedwith a predefined group of multicast addresses. Each NMM in the networkshould receive the Hello message which contains the address of the NMMwhich originated the message. The Hello messages contains informationregarding the model and revision number of the originating NMM asdescribed in connection with FIG. 11 ()ines 134, 132). This latterinformation Will be used to distinguish between Model 1000 and 3000 NMMs(and concentrators).

Each concentrator should receive a Hello message from each of the otherconcentrators in the network. A Model 3000 has the capability ofmonitoring the particular port over which the Hello message is received,as previously described. Model 1000 concentrators can only distinguishbetween Up Port and Down Port messages.

Each NMM maintains an internal list or table of the port-slot and NMMaddress for each of the received Hello messages. If the NMM is a Model1000 the "port-slot" will be either Up Port or Down Port. For example,for the configuration shown in FIG. 12, concentrator 106 having NMMaddress "05", has direct connection to the three other concentrators.Concentrator 112, having address 06, is connected to concentrator 106 atslot 3, port 2 (3-2). Concentrator 114, having address 08, is connectedto slot 6, port 1 (6-1) of concentrator 106. Finally, concentrator 100,having address 03, is connected to slot 4, port 2 (4-2) of concentrator106.

Once concentrator 106 has received a Hello message originating from eachconcentrators in the network, it will construct an NMM list. The listwill have a total of seven entries since there are seven otherconcentrators in the network. The NMM list will reflect that a Hellomessage from concentrator address 06 was received over slot 3, port 2(3-2), and that another Hello message originating from concentratoraddress 08 was received over slot 6, port 1 (6-1). Finally, the listshould further reflect that Hello messages originating from theremaining five concentrators were received on slot 4, port 2 (4-2) ofconcentrator 106.

FIG. 13 is on NMM List table containing the NMM list for all of theconcentrators of the FIG. 12 network. The left column, the "ReportingConcentrator Address" column, contains the address of each of thereporting concentrators. The middle column, the "Slot-Port" column,contains the slot and port over which Hello messages were received. Theright column, the "Concentrators Heard" column, contains theconcentrator address which indicates the address of the concentratorwhich originated the Hello message.

The NMM entry in the NMM List table for concentrator 106, which hasaddress 05, indicates that Hello messages originating from the remainingseven concentrators were received over three separate ports (3-2, 6-1and 4-2), as previously described. This information is collected andstored in concentrator 106, to be eventually forwarded to the CCA 93c.Similarly, concentrator 104, having address 01 received all sevenmessages over a single port, namely slot-port 2-1. This information isalso collected and stored in concentrator 104 to be forwarded to theCCA. The other concentrators collect and store similar information ascan be seen in the NMM List table of FIG. 13.

Each concentrator has only limited information concerning the topologyof the network. For example, concentrator 106 (address 05), canascertain that it received Hello messages from five concentrators overslot-port 4-2. However, the concentrator is unable to ascertain theactual path taken over the network by the Hello messages. For example,concentrator address 05 cannot ascertain that the Hello messageoriginating from concentrator 104 (address 01) was forwarded byconcentrator 100 (address 03) instead of taking some other path, such asa direct path.

Although the NMM list of a particular concentrator does not containsufficient information to create the network topology, the totalinformation in the NMM tables created by each of the concentrators doescontain sufficient information. As will be described, this informationis collected from the NMMs by the CCA in a format such as the FIG. 13NMM List table to create the overall network topology.

The CCA monitors the various Hello messages transmitted by each NMM inthe network. The CCA creates a table, such as the FIG. 16 AncestorTable, which initially only includes the NMM addresses of all of theconcentrators in the Network. The NMM addresses are used to allocatememory for creating the Ancestor Table. The CCA also determines whichNMM and associated concentrator will become the root of the topologytree. The NMM List table will also contain information (not depicted)regarding the particular type of NMM so that the CCA can distinguishbetween Model 1000 and 3000 NMMs.

FIG. 14 is a block diagram of the process after the Hello PDUs have beenreceived by the CCA which contain the addresses of the reportingconcentrators. The diagram illustrates the manner in which the CCAobtains information from the concentrators to complete the Link Table ofFIG. 13. Element 118 of FIG. 14 represents the block request transmitprocess where the CCA transmits a separate message N1-Nn, represented bylines 122, to each of the concentrators in the network 120 for which aHello PDU was received. The messages request that the concentratorsprovide the CCA with the NMM list associated with the concentrator.

Each of the messages of the block request is referred to as a Get NMMList message and the messages are transmitted sequentially over thenetwork, preferably back-to-back. The concentrators in the network 120respond to the Get NMM List messages by transmitting back to the CCA anNMM List PDU, represented by lines 24. The NMM List PDU contains NMMList of the reporting concentrator. As previously described, the listcontains the addresses of the concentrator received by the reportingconcentrators and the slot-port over which the messages are received.

The NMM List PDUs may be received and processed by the CCA, asrepresented by block 126 in any order. It is possible that some of theconcentrators will not respond to the Get NMM List PDU for some reason.In that case the returned messages Nr will be less than the transmittedmessages Nl-Nn. As indicated in block 126, the CCA monitors the numberof response by incrementing an NMM List received counter.

The CCA will monitor the received NMM Lists. If the CCA fails to receivean NMM List from one or more concentrators, the CCA will wait apredetermined period of time. Once the period of time has expired, asrepresented by element 128, the CCA will issue a further block requestcomprising Get NMM List PDUs separately directed to the concentratorswhich have not responded or which have been dropped in the CCA ordropped somewhere in the network. This is a connection list protocol sothat delivery of a message is not assured. The message could have beeninvolved in a collision, for example. This process is repeated a maximumof five times, as indicated by element 130. If the maximum number ofretries is exceeded, an error message is issued as shown by block 132.

A determination is then made as to, as indicated by element 136, whetherthe CCA has received a NMM list from all of the concentrators in thenetwork which are to be included in the topology. The process carriedout by the CCA utilizing the NMM List data is represented by the flowdiagram of FIG. 15. The results of the process are shown in the AncestorTable of FIG. 16, as will be explained.

Each NMM sends its link information to the CCA in the format given inFIG. 13. The link data is also known as the NMM List. The link data arearranged by slot/port group. For example, in FIG. 13, the NMM withaddress 05 sends three groups of link data, one group associated withslot-port 3-2, another associated with slot-port 6-1, and the lastassociated with slot-port 4-2. The CCA processes each list using thefollowing method. The CCA searches through each slot-port group for thepresence of the root NMM, which had been previously selected. If theRoot NMM exists in that group, the slot-port number is entered in the"Own-Slot-Port" field of the Ancestor Table, such as the NMM atconcentrator address 05 in FIG. 16. However, if the Root NMM is notpresent in the slot-port group, the CCA accesses the "Ancestor" field ofeach group member in FIG. 16 and enters the address and slot-portnumbers of the reporting NMM. That is, the reporting NMM becomes one ofthe ancestors for NMMs existing in slot-port groups not containing theRoot NMM.

The CCA processes these lists on-the-fly, and discards the data. Thereis no requirement to save individual NMM link data, which can exceed1200 bytes for a large network.

Block 138 of FIG. 14 is executed after all NMM lists are received andprocessed by the CCA. This block checks the Ancestor Table of FIG. 16,and resolves immediate parent-child relationships of each NMM. Theparent of an NMM is the ancestor of the NMM which is one level lowerthan itself. Note that the Root NMM does not have any ancestors.

As previously described, the topology depicted in the Network ManagementControl Console NMCC display includes various concentrators connected inan inverse tree hierarchy. The highest level of the hierarchy, Level 0,contains a single root concentrator. Level 1 contains the concentratorin the next from highest level and so forth.

It should be noted that there is not necessarily a unique topologydisplay for a particular network configuration. For example,concentrator 100 shown in FIG. 12 is shown at the top of the networkhierarchy but the topology could be drawn with another concentrator asthe root concentrator.

The CCA selects one of the concentrators to be the root concentratorbefore requesting the NMM List for the concentrator.

If the network is comprised exclusively of Model 1000 NMMs, the CCAselects the concentrator with the largest number of Down Port links asthe root concentrator. This will also be the one concentrator with no UpPort links, with one exception. It is possible that more than oneconcentrator having a Model 1000 is connected by way of the Up Port. Forexample, in FIG. 17, there are three concentrators, 116a, 116b and 116c,connected by way of the Up Port link. In that event none of theconcentrators will be selected as the root. A dummy concentrator will beassigned the root position (a virtual root) and the actual concentrators116 will be assigned to the Level 1 and lower hierarchy levels.

If the network includes only concentrators having Model 3000 NMMs, anyof the concentrators can be selected as the root. However, the CCAselects the concentrator with the maximum number of links.

Assuming that the network includes concentrators having both Model 1000and 3000 NMMs, a concentrator having a Model 1000 NMM, with no otherconcentrator having a Model 1000 NMM linked to the Up Port, will beselected as the root. Although any concentrator having a Model 3000 NMMlocated on the Up Port side of the highest level Model 1000 NMM couldalso be selected, this information is not available to the CCA from thenetwork.

In the present example, concentrator 102 having a concentrator address02 is selected as the root of the network because it is the onlyconcentrator having a Model 1000 NMM at this early stage of theprocessing.

Returning to the FIG. 15 flow chart, once the root concentrator isselected, one block of entries is taken from the NMM List of FIG. 13 asindicated by element 146 of the chart. An entry is defined herein as theaddress of a particular concentrator heard over a particular slot-portof the reporting concentrator. A block of concentrator entry means allof the concentrator addresses heard over a particular slot-port. Forexample, in the NMM List of FIG. 13, reporting concentrator address 03has three blocks of entries. The first block includes the address of theconcentrators heard over slot-port 2-1, including address 02, 07 and 04.

Assume that the first block of entry for concentrator 03 has beenobtained. The next step is to determine whether the block contains theaddress of the previously-selected root concentrator, as indicated byelement 148.

Each reporting concentrator will receive message from all concentrators,including the root concentrator. The block of entries for slot-port 2-1of concentrator address 03 includes root concentrator address 02. Asindicated by element 150 in the flow chart, the slot-port over which thereporting concentrator receives messages from the root concentrator isadded to the Root column of the FIG. 16 Ancestor Table. Thus, entry"2-1" is added to the Root column for reporting concentrator address 03.

Once the slot-port has been added, a determination is made as to whetherall blocks have been processed or updated, as shown by element 160. Inthe present case, only a single block has been processed, therefore thenext block of entry from the Link Table of FIG. 13 is processed, asrepresented by blocks 162 146.

The next block includes one entry, address 01, which indicates that thereporting concentrator address 03 received messages from concentratoraddress 01 over slot-port 3-2. This information indicates that reportingconcentrator address 03 must be used by concentrator address tocommunicate with the root concentrator. In other words, reportingconcentrator address 03 is an "ancestor" of concentrator address 01. Ifconcentrator 01 is connected directly to concentrator 03, concentratoraddresses 03 and 01 have a "parent"--"child" relationship, respectively.At this point in the processing, there is only enough information toindicate that an ancestor relationship exists between the twoconcentrators.

As shown by block 152, the address of the entry is obtained, address 01,so that the appropriate location in the Ancestor Table of FIG. 16 islocated. Next, the address of the reporting concentrator, 03, is enteredin the Ancestor column associated with concentrator 01, therebyindicating that concentrator address 03 is an ancestor of concentratoraddress 01. The slot-port showing the connection to the ancestorconcentrator, 3-2, is added to the slot-port column of the Table.

The Level column in the Ancestor Table indicates the level of theassociated concentrator in the network hierarchy. The level is initiallyset to zero for all of the concentrators. Only the root concentratorwill remain at Level 0.

Since concentrator address 01 is below concentrator 03 in the hierarchyof the network, it is known that the concentrator address 01 cannot beat Level 0. The value of the level entry for concentrator address 01 isincreased by one, as indicated by block 156. Eventually, the level foraddress 01 will be increased to two, as shown in the Table.

Next, a determination is made as to whether all the entries for theblock have been processed or updated as shown by element 158. In thepresent example, there was only one entry in the second block.Accordingly, the next block of entry for reporting concentrator address03 is obtained. This block contains three entries, includingconcentrator addresses 05, 06 and 08 which transmitted messages receivedby reporting concentrator 03 over slot-port 4-1.

The entry does not contain the root concentrator at address 02 (element148). Accordingly, the address for the first entry of the block, address05, is read so that the appropriate location in the Topology Table isfound. Next, the reporting address 03 is entered in the Ancestor columnof the Table together with the slot-port 4-1. The level number foraddress 05 is increased by one (block 156) and a determination is madeas to whether all entries for the block have been processed (element158).

Since the block contains the two additional entries, addresses 06 and08, these entries are then processed. Concentrator address 03 is enteredas an ancestor to concentrator 06 together with the slot-port 4-1 (block154) and the level is increased by one. Concentrator address 03 is thenentered as an ancestor for concentrator address 08 together withslot-port 4-1. Again, the level number for address 08 is increased byone.

Once all of the entries for the block have been processed (element 160),the next block of entries is obtained (block 146). There is one block ofentries associated with reporting concentrator 04 in the NMM List. Sincethe block contains the root concentrator address 02, the slot-port 3-1is entered in the Root column of the Topology Table (block 150). Allblocks of entry have been processed (element 160), therefore, the nextblock is obtained.

The process is repeated for the three blocks of entry for reportingconcentrator addresses 01, 08 and 06. In each case, the block containsthe root concentrator so the slot-port over which the root concentratoris heard is added to the "Own Slot-Port" column of the Ancestor Table.Thus, slot-port 2-1, 3-1, and 2-6 are inserted in the Root column forreporting concentrators 01, 08 and 06, respectively.

Reporting concentrator address 05 in the NMM List includes three blockson entry. The process is repeated with concentrator address 05 beinginserted in the Ancestor Table as an ancestor to concentrator 06 and 08together with port-slot 3-2 and 6-1, respectively (block 154). The levelnumbers for the two addresses are also increased by one (block 156).

The next entry for reporting concentrator 05 indicates that the rootconcentrator address 02 is heard by concentrator address 05 overport-slot 4-2. That entry is made (block 150) in the Root column of theAncestor Table at concentrator address 05.

The next block of entry is for root concentrator address 02. Bydefinition, all concentrators are descendants of the root concentrator.Accordingly, the root concentrator address 02 will be inserted as anancestor for each of the seven other concentrators, together with theassociating slotports. Since the root concentrator is a Model 1000concentrator, the slot-port will be either Down or Up. In addition, thelevel for each of the concentrators, other than the root concentrator,will be increased by one.

The last block of entry is for concentrator address 07. The blockcontains the root concentrator, so the slot-port, 4-7, is entered (block150) in the Root column of the Topology Table. As indicated by element160, all blocks of the Link Table will have been processed or updated.Accordingly, the information in the Link Table is no longer needed andthe Table is discarded, as represented by block 164.

Information in the FIG. 16 Ancestor Table is then used to create adisplay of the actual network topology. The Level column of the Tablewill have been increased each time an ancestor is added so that thefinal value accurately reflects the level of the concentrator in thenetwork. It is then possible to distinguish parent concentrators fromother ancestor concentrators. For example, concentrator address 01 hastwo ancestor, and is, therefore, at level 2. The ancestors includeaddresses 03 and 02. Concentrator address 03 is at Level 1 and address02, the root concentrator, is at Level 0. Accordingly, concentrator 03is the parent concentrator of concentrator address 01.

The information in the Ancestor Table, together with the informationregarding the model number of the concentrator, is then forwarded to theUser Interface of the Network Management Control Console to create thenetwork topology display. A somewhat simplified display topology imageis depicted in FIG. 18 which is generally designated by the numeral 137.The topology image is based upon the exemplary network of FIG. 12. Notethat the actual display will show only two levels of concentrators,rather than the three levels depicted.

Level 1 shows the icon for the root concentrator address 02. The iconindicates that there are three levels of concentrators below Level 0 andthere are a total of seven concentrators below.

The Level 1 icons depict the concentrator addresses 03, 04 and 07. Thelinkage symbol for address 03 indicates that the concentrator isconnected from port 1, slot 2 of the Model 3000 concentrator to theBackplane (BK PL) of the Model 1000 root concentrator at address 02. Theup link for address 03 is from a particular port, port 1, of the modulelocated in slot 2 of the concentrator. The up link could also have beenmade from the Network Management Module NMM of the concentrator. Since aNMM has only a single port, only the slot number of the NMM in theconcentrator would be depicted in the linkage symbol.

The CCA will automatically update the Network Topology Table of FIG. 16should the configuration of the network changes. For example, if aconcentrator is added by connecting it to slot-port 4-8 of concentratoraddress 07 of FIG. 12, the presence of the new concentrator would bedetected and the topology display updated.

As previously described, the CCA monitors the Hello PDUs from every NMMin the network. If three consecutive Hello PDUs are missed from aparticular NMM, the NMM is treated as missing and a warning message issent to the User Interface for display.,

Similarly, if three consecutive Hello PDUs are missed from a particularNMM of a concentrator, the NMM is aged out of the NMM list in the LinkTable. The NMM is also issued a Kill NMM PDU by the other NMMs. If theNMM of the concentrator responds, it will transmit what is called a NewHello PDU and will rejoin the network as a new concentrator. Thisprocedure ensures that the CCA can detect any changes in concentratorconnectivity.

An NMM in the network will transmit a Hello PDU in any of the threesituations. First, a Hello PDU will be transmitted after the NMM hasreceived down loaded code from the CCA. Second, an NMM will issue aHello PDU if the NMM fails to receive three consecutive CCA LoadserverReady PDUs which, as previously noted, indicate to the NMMs that the CCAis ready to download code to the NMM. Finally, an NMM will transmit theHello PDU after it receives a Kill NMM PDU.

When the CCA detects a New Hello PDU, it commences an update of thenetwork topology. If the number of new concentrators is relativelysmall, less than ten, the CCA updates each NMM location in the topologytree by using a binary search method. First, the CCA compiles a table ofnew concentrators. The CCA then requests the root concentrators for itsNMM list.

If a new NMM is present in the root NMM list, the NMMs in the next leveldown are requested to provide the associated NMM list. This process isrepeated until the NMM list from the reporting concentrator indicatesthe presence of only the new NMM over that port.

If more than ten new NMMs have been added to the network, it is moreefficient to simply rebuild the topology as previously described.

The Network Management Modules (NMMs) and the Control Console Adapter(CCA) can be implemented in a variety of ways to carry out thepreviously described functions. Since the particular details regardingthe construction of the NMM and the CCA form no part of the presentinvention, the NMM and the CCA will only be briefly described.

FIG. 19 is a functional block diagram of the Network Management Module(NMM). The NMM includes a microprocessor 166, such as a microprocessormanufactured by NEC having the designation V35. The microprocessorincludes a core 168 and service port 170. A serial port 172 is providedfor connecting the NMM to a modem for out of band (external to thenetwork) control of the NMM.

The microprocessor is coupled to a multiplexed address output bus 176and a data bus 178. An address buffer 177 is provided for storing theupper byte of address so that the full address can be used for dynamicrandom access memory (DRAM) 180, programmable read only memory (PROM)182 and static random access memory (SRAM) 184.

PROM 182 is a boot memory and DRAM 180 holds the code for the individualNMMs which is downloaded by the CCA to the NMM over the network. SRAM184 is used to hold frames of the data either received from the networkor to be transmitted over the network.

Block 192, collectively representing miscellaneous control circuitry,including SRAM access control, data bus control, memory I/0 decodes,various counters, special functions and various glue logic.

The data and address busses are coupled to a conventional networkinterface controller (NIC) 188, such as the controller marketed byNational Semiconductor under the designation DP8390/NS32490. The NIC 188is for interfacing with CSMA/CD type local area networks such asEthernet. The NIC functions to receive and transmit data packets to andfrom the network and includes all bus arbitration and memory supportlogic on a single chip.

The NIC has a single bus 189 which serves both as an address bus and adata bus. Latch 186 is used to hold the addresses for the NIC andaddresses from the NIC. A data buffer 179 functions to isolate the databus 178 of the processor from the NIC bus 187 and also functions toprovide some bus arbitration features.

The NMM further includes a serial network interface (SNI) 190. SNI 190can be an interface device marketed by National Semiconductor under thedesignation Dp8391/NS32491. The CSMA/CD data on the network and backplane bus 84 are Manchester encoded, and the SNI performs Manchesterencoding and decoding functions.

The SNI receives the encoded data from the data steering logic (DSL) 90which receives the CSMA/CD data from the CSMA/CD backplane bus 84 forforwarding to SNI 190 In addition, DSL 90 transmits CSMA/CD data fromthe SNI to the CSMA/CD bus. The data steering logic SLD 90 responds toand controls a status line 93 which is used to control the mode of theNMM. The NMM has various modes of operation wherein the NMM can act as aprimary NMM for the concentrator, a backup NMM for the concentrator anda partition mode. In the partition mode the NMM can be isolated(partitioned) from the CSMA/CD bus 84 or isolated (partitioned) from theNMM up port connection in response to commands from the CCA.

The NMM further includes a repeater and retiming unit (RRU) 92, aspreviously explained, which repeats the CSMA/CD data received on bus 84by way of the data steering logic 90. The RRU also retimes the data fortransmission back to the CSMA/CD bus 84 and for transmission on the NMMUp Port by way of a medium dependent adapter (MDA) 198. MDA 198 alsoreceives CSMA/CD data from the Up Port connection for retransmission onthe CSMA/CD bus 84.

The data bus 178 is also connected to the Network Management Interface(NMI) 106 which provides the interface between the NMM and the backplanecontrol bus. As previously described in connection with the descriptionof FIGS. 10 and 11, the NMI 106 cooperates with the NMIs 107 in the hostmodules.

The NMI 106 of the NMM provides two functions. First, the NMI 106 isimplemented to have the same circuitry as the NMI 107 used in the hostmodules as depicted in FIG. 11. This circuitry is used to provide backupNMM status similar to host module status, to the primary NMM. Second,the NMI 106 is implemented to provide control signals for control bus86. The control bus delivers commands sent by the NMM to the host moduleand further provides the response from the host module back to the NMM.

As previously described, the NMM can issue either control commands orstatus commands to a particular host module in the concentration. Thespecific module (slot location) will decode the command and take action.The command transmitted over the control bus from the NMM NMI 106 andthe responses from the host module NMI 107 are on eight lines of the buswhich carry signals NMIDAT (FIG. 11). NMI 106 also produces the threecontrol signals RD/WRL, DAT/CMDL and DENL which are used by the hostmodule NMI 107 for receiving the commands and transmitting the responseback to the NMM NMI 106.

The control console adapter CCA is similar to the NMM as can be seen inthe functional block diagram of FIG. 20. Functional elements common tothe CCA and NMM are designated with the same numerals. The CCA isfunctionally an intelligent Ethernet card. The serial network interfaceSNI 190 is connected to a fifteen pin electrical connector 191. Theinterface of the CCA with the network is simpler than the networkinterface of the NMM since the NMM must function with a CSMA/CD bus 84whereas the CCA need only connect to a single network port. Theconnector 191 is typically coupled to an off card transceiver or mediaaccess unit (MAU) (not depicted) by way of an off card attachment unitinterface (AUI).

The data bus 179 of the CCA is connected to a personal computer PC I/0circuitry 83. I/0 circuitry 183 is coupled to the PC bus 97 and to thegraphical user interface UI (the windows interface) of the PC by way ofa memory resident interface (MRI) which is not depicted.

Although the CCA provides processing capability, it is possible to use aconventional Ethernet card with the processing function of the CCA beingcarried out by the processor and associated memory in the personalcomputer of the NMCC.

The User Interface in the Network Management Control Console alsogenerates the expanded view of a particular concentrator front panel, asshown in FIGS. 7 and 9 utilizing data provided by the individual NMMs.Each NMM is capable of determining the configuration of the concentratorin which it is located by way of the control bus 86 (FIG. 10) of theconcentrator back plane. As previously described, the NMM can ascertainwhich slots in the concentrator are occupied and, if occupied, the modeland revision of the module which is located in the slot.

When the user selects a particular concentrator to be displayed in theexpanded view window, the CCA requests status information regarding theconcentrator from the associated NMM. Data regarding the model type andrevision of each module in the concentrator, including the reportingNMM, and the location of the modules in the concentrator, are forwardedto the CCA. The bit mapped graphics are stored in the personal computerdata base of the NMMCC. The appropriate bit map data can then be used toproduce the concentrator image utilizing a conventional windows graphicuser interface having graphics capability such as Microsoft Windows.

As previously explained, the various modules have one or more LEDs whichprovide miscellaneous status information. The expanded view image of theconcentrator will reflect the actual status of an LED by eitherdisplaying a particular color area at the LED image location (to showillumination) or by displaying a black area (to show lack ofillumination). The CCA will request that the NMM of a particularconcentrator issue a command to the host modules in the concentrator,soliciting LED status information. The information is forwarded to theCCA and used by the interface to control the appearance of the LEDimages to reflect the actual status of the LEDs.

The foregoing can be further illustrated by the flow charts depicted inFIGS. 21A-21C. In FIG. 21A, block 200 indicates that the user firstutilizes the mouse to select the particular concentrator to bedisplayed. Next, block 202 shows that the window graphic user interfacecreates the expanded view process/window.

The User Interface UI then obtains the module type data from the dataattached to the concentrator child window as shown by block 204. The UIthen obtains from its own data base, using the module type and revisionnumber, the detailed module data including, for example, data fordepicting the indicia of module model number, LED location, portlocation, and so forth, such as depicted in FIGS. 7 and 9.

The graphics bit map for the concentrator image is loaded and displayedon the NMCC screen, as indicated by block 208. Finally, a message issent to the expanded view process to update itself with LED statusinformation thereby concluding the process, as shown by elements 210 and212.

The FIGS. 21B and 21C flow charts relate to the LED status updatesequence. Block 214 of FIG. 21B indicate that a message is received bythe expanded view process to update itself with LED status. The NMCCthen transmits an LED STATUS PDU over the network to the appropriateconcentrator (Block 216). The concentrator NMM will respond with 32 bitsof encoded data for each module in the concentrator. Each bit of thedata is capable of indicating the status of an LED in the module, with a"1" indicating that the LED is illuminated and a "0" indicating that theLED is off.

Block 220 of FIG. 21C indicates that the LED status data are received bythe NMCC from the NMM of the concentrator over the network. Therectangular locations in the bit mapped graphics for the LED are thenfilled with the appropriate color (or black) based upon the receiveddata thereby concluding the update (elements 222 and 224).

Thus, a novel apparatus and method have been disclosed to generate thetopology of a network and to display an image of a concentrator whichaccurately depicts the state of the concentrator. While the inventionhas been described in some detail it is to be understood that thoseskilled in the art can make certain changes in the actual implementationwithout departing from the spirit and scope of the invention as definedin the following claims.

We claim:
 1. Apparatus for monitoring the status of a star configuredlocal area network having hubs, with a hub including a chassis forreceiving a plurality of modules of varying type, each of the moduleshaving at least one port for connecting a data terminal device to thehub, said apparatus comprising:means for generating a topology of saidnetwork and for receiving topology data from a reporting hub whereinsaid topology data comprises addresses of other hubs which originatedmessages received by said reporting hub over a particular port of saidreporting hub and an indentifier of said particular port; location meansfor producing location data indicative of the location of each of themodules and each of the at least one port associated with the modules inthe hub chassis; type means for producing type data indicative of thetype of each of the modules and each of the at least one port associatedwith the modules in the hub; indicator means for indicating statusinformation about each of said modules and for indicating statusinformation about said at least one port associated with each of saidmodules, said indicator means also for isolating said status informationfor one particular module and associated at least one port, saidindicator means coupled to said location means and also coupled to saidtype means; modification means for modifying port status of each of saidat least one port associated with each of said modules, saidmodification means responsive to a user input, said modification meanscoupled to said indicator means; and display means for producing animage of the hub utilizing said location data, said status informationand said type data, with the image depicting the location of the modulesin the hub and the type of modules, said display means coupled to saidindicator means.
 2. The apparatus of claim 1 wherein said display meansincludes storage means for storing a set of graphic data representing agraphic image for display on said display means, for each of the typesof modules, which represents the appearance of the modules.
 3. Theapparatus of claim 2 wherein said modules include a front panel whichbears an indicia of the type of module and said set of graphic data,representing a graphic image for display on said display means, includedata which represents said indicia.
 4. The apparatus of claim 2 whereinsaid set of graphic data include data which represents an image of theat least one port of the modules.
 5. The apparatus of claim 2 whereinone type of the modules has at least one port with an optical connectorfor receiving an optical cable and wherein said set of graphic datainclude data which represent an image of said optical connector.
 6. Theapparatus of claim 2 wherein one type of the modules has at least oneport with an electrical connector for receiving an electrical cable andwherein said set of graphic data include data which represents an imageof said electrical connector.
 7. The apparatus of claim 2 wherein saidindicator means of one type of the modules includes a front panel whichhas a light source which indicates the status of the module and thestatus of said at least one port associated with each of said modulesand wherein said set of graphic data include data which represents animage of the light source.
 8. The apparatus of claim 7 wherein saidindicator means includes a light source status means for producing lightsource status data indicative of the state of the light source andwherein said display means utilizes said status data to control theimage of the light source.
 9. The apparatus of claim 1 wherein saidlocation means, said indicator means and said type means are disposed atthe hub.
 10. The apparatus of claim 9 wherein said display means isdisposed separate from the hub.
 11. The apparatus of claim 2 whereinsaid set of graphic data include data which represents an image of theat least one port of the module and wherein said indicator means of saidapparatus further includes:pointer means for designating a particularlocation on the image selected by a user; module status means forproducing module status data indicative of the status of the modules;port status means for producing port status data indicative of thestatus of the port of the modules; and control means coupled to saidmodification means for selectively producing said module status data ofa particular module when a user designates the image of said particularmodule utilizing said pointer means and for selectively producing saidport status data of a particular port when a user designates the imageof said particular port utilizing said pointer means.
 12. A method ofmonitoring the status of a star configured network having hubs, with ahub including a chassis for receiving a plurality of modules of varyingtype, with each of the modules having at least one port for connecting adata terminal device to the hub, said method comprising the followingsteps:generating a topology of said network by receiving topology datafrom a reporting hub wherein said topology data comprises addresses ofother hubs which originated messages received by said reporting hub overa particular port of said reporting hub and an indentifier of saidparticular port; generating and reporting by a hub location dataindicative of the location of each of the modules and ports in the hubchassis; generating and reporting by the hub type data indicative of thetype data indicative of the type of each of the modules and ports in thehub; and producing an image of the hub utilizing said location data andsaid type data, with the image depicting the location of the modules inthe hub and the type of modules in the hub.
 13. A method ofautomatically determining the topology of a network of interconnectedhubs which utilize contention control, with each of the hubs havingmodules and associated at least three data ports, each of which is forcoupling the hub in a star configuration to either a data terminaldevice or another hub of the network, said method comprising thefollowing steps:transmitting from each of the hubs a message over thenetwork which originates from the hub and which contains an addressidentifying an associated hub; transmitting from each of the hubs amessage over the network which was received by said associated hub fromanother hub on the network which originated the received message;identifying, at each of the hubs, which of the data ports of saidassociated hub has received one of the messages transmitted by anotherhub of the network; receiving topology data from each of the hubs, withthe topology data identifying a particular one of the data ports of aparticular reporting hub and receiving addresses of the other ones ofthe hubs which originated messages received by said particular reportinghub over the particular port; determining the overall topology of thenetwork utilizing said combining each of said received topology data;and displaying said overall topology on a display device, said step ofdisplaying including displaying multiple hubs, modules and associatedports on said display device at the same time.
 14. Apparatus forautomatically determining the topology of a local area network ofinterconnected hubs which utilize contention control, with each of thehubs having at least three data ports, each of which is for coupling thehub in a star configuration to either a data terminal device or anotherhub in the local area network, said apparatus also for monitoring thestatus of a hub of a star configured local area network, with the hubincluding a chassis for receiving a plurality of modules of varyingtype, each of the modules having at least one port for connecting a dataterminal device to the hub, said apparatus comprising:transmit means ateach of the hubs for transmitting hub messages over the local areanetwork, said transmit means including(a) originate means fortransmitting said hub messages which originate at an associated hubwhich contain an identifying address of said associated hub; (b) repeatmeans for transmitting said hub messages received by said associated hubover the local area network which originated from other ones of saidhubs of the network, said repeat means comprising a timing unit forretiming data to account for transmission distortion; port identifyingmeans at each of the hubs for identifying which of said data ports ofsaid associated hub has received one of the said hub messagestransmitted by another of said hubs of the local area network; controlmeans coupled to said local area network for receiving topology datareported from each of said hubs, said topology data reported for eachdata port of a particular reporting hub, said topology data identifyinga particular one of said data ports of said particular reporting hub andsaid topology data identifying addresses associated with the the otherports of said hubs which originated network messages received by saidparticular reporting hub over said particular port; processing means fordetermining the overall topology of the local area network utilizing andcombining said received topology data; location means for producinglocation data indicative of the location of each of the modules andports in the hub chassis based on said overall topology; type means forproducing type data indicative of the type of each of the modules andports in the hub; and indicator means for indicating status informationabout each of said modules and for indicating status information aboutsaid at least one port associated with each of said modules, saidindicator means also for isolating said status information for oneparticular module and associated at least one port, said indicator meanscoupled to said location means and also coupled to said type means;modification means for modifying port status of each of said at leastone port associated with each of said modules, said modification meansresponsive to a user input, said modification means coupled to saidindicator means; and display means for producing an image of the hubutilizing said overall topology, said location data, said statusinformation and said type data, with the image depicting the location ofthe modules in the hub and the type of modules, said display meanscoupled to said indicator means.
 15. The apparatus of claim 14 whereinsaid display means includes storage means for storing a set of graphicdata representing a graphic image for display on said display means, foreach of the types of modules, which represents the appearance of themodules and wherein said set of graphic data include data whichrepresents an image of the at least one port of the modules.
 16. Theapparatus of claim 15 wherein said set of graphic data include datawhich represents an image of the at least one port of the module andsaid indicator means of said apparatus further includes:pointer meansfor designating a particular location on the image selected by a user;module status means for producing module status data indicative of thestatus of the modules; port status means for producing port status dataindicative of the status of the port of the modules; and control meansfor selectively producing said module status data of a particular modulewhen a user designates the image of said particular module utilizingsaid pointer means and for selectively producing said port status dataof a particular port when a user designates the image of said particularport utilizing said pointer means.
 17. Apparatus for automaticallydetermining the topology of a local area network of interconnected hubswhich utilize contention control, with each of the hubs having at leastthree data ports, each of which is for coupling the hub in a starconfiguration to either a data terminal device or another hub in thelocal area network, said apparatus also for modifying status informationwith associated with said ports of said interconnected hubs, saidapparatus comprising:transmit means at each of the hubs for transmittinghub messages over the local area network, said transmit meansincludingoriginate means for transmitting said hub messages whichoriginate at an associated hub which contain an identifying address ofsaid associated hub; repeat means for transmitting said hub messagesreceived by said associated hub over the local area network whichoriginated from other ones of said hubs of the network, said repeatmeans comprising a timing unit for retiming data to account fortransmission distortion, port identifying means at each of the hubs foridentifying which of said data ports of said associated hub has receivedone of the said hub messages transmitted by another of said hubs of thelocal area network; control means coupled to said local area network forreceiving topology data reported from each of said hubs, said topologydata reported for each data port of a particular reporting hub, saidtopology data identifying a particular one of said data ports of saidparticular reporting hub and said topology data identifying addressesassociated with the other data ports of said hubs which originatednetwork messages received by said particular reporting hub over saidparticular one of said data ports; processing means for determining theoverall topology of the local area network by utilizing and combiningsaid received topology data from each of said reporting hubs; statusindicator means for indicating status information of said data ports ofeach of said hubs in said overall topology, said status indicator meansalso for isolating a particular data port status information;modification means for changing said status information of said dataports of each of said hubs, said modification means coupled to saidstatus indicator means and responsive to a user input device; anddisplay means for displaying said overall topology in a graphic imageformat on a display device
 18. The apparatus of claim 17 wherein saidoriginate means periodically transmits one of said hub messagesoriginating at said associated hub.
 19. The apparatus of claim 17wherein said control means receives said topology data in response totopology request messages which the control means transmits over thelocal area network to the hubs and wherein said control means transmitsseparate ones of said topology request messages to each of said hubs.20. The apparatus of claim 19 wherein said control means monitors whichof said hubs has responded to said topology request message andtransmits additional topology request messages directed to any of thehubs for which a response in said topology data is not received by saidcontrol means.
 21. The apparatus of claim 17 wherein each of said hubsincludes a plurality of modules, with each of said modules having atleast one of said data ports and wherein said hub includes monitoringmeans for identifying a particular one of said modules and a particulardata port of said modules over which said hub has received said hubmessages originating from other one of said hubs in the local areanetwork.
 22. The apparatus of claim 21 wherein said modules and dataports are of different types having varying capabilities and whereinsaid monitoring means is also a means for identifying said type ofmodule and data port and wherein said topology data further includestype data indicative of the type of modules and data ports in saidparticular reporting hub.
 23. The apparatus of claim 22 wherein saidmonitoring means identifies a particular one of said modules and aparticular one of said data ports by determining a physical location ofsaid module in said hub; wherein said status indicator means indicatesthe status of said data ports of said particular one of said datamodules; and wherein said modification means allows modification of saidports of said particular one of said modules.
 24. The apparatus of claim23 wherein said hub includes a chassis having an electrical backplanefor interconnecting said modules and said modules may be inserted insaid chassis in any one of predetermined locations along said backplane,with said monitoring means determining said physical location by sensingthe predetermined location where said modules are inserted.
 25. A methodof monitoring the status of a hub of a star configured network inaccordance with claim 12 further comprising the step of providingmodification to said ports of said modules based on said image of saidhub and responsive to a user input
 26. The method of claim 12 whereinsaid step of producing an image comprises the step of displaying a setof graphic data representing a graphic image for each of the types ofmodules, which represents the appearance of the modules.
 27. The methodof claim 26 wherein said modules comprise a front panel which bears anindicia of the type of module and said set of graphic data includes datawhich represents said indicia.
 28. The method of claim 12 wherein saidstep of producing an image comprises the step of displaying a set ofgraphic data representing a graphic image for at least one port of themodules.
 29. The method of claim 28 wherein one port comprises anoptical connector for receiving an optical cable and wherein said set ofgraphic data include data which represent an image of said opticalconnector.
 30. The method of claim 28 wherein one port comprises anelectrical connector for receiving an electrical cable and wherein saidset of graphic data include data which represent an image of saidelectrical connector.
 31. The method of claim 12 further comprising thestep of generating status data indicating status of the modules andports of the hub and wherein said step of producing an image of said hubfurther comprises the steps of:displaying a set of graphic datarepresenting a front panel of a module of the hub which has a lightsource which indicates the status of the module; and displaying a set ofgraphic data representing the status data of said at least one portassociated with each module.
 32. The method of claim 12 furthercomprising the steps of:generating status data indicating status of themodules and ports of the hub; providing pointer means for designating aparticular location on the image for selection by a user; selectivelydisplaying a set of graphic data representing module status data of aparticular module when a user designates the image of said particularmodule utilizing said pointer means; and selectively displaying a set ofgraphic data representing port status data of a particular port when auser designates the image of said particular port utilizing said pointermeans.